1. Field of the Invention
The present invention relates to a signal transmission structure, more particularly, the present invention relates to a signal transmission structure of preventing an internal signal thereof from Electromagnetic Interference (EMI).
2. Description of Related Art
At present market, an electronic apparatus having a signal transmission structure therein is utilized to transmit signals in the electronic apparatus. In general, there is a high-density electronic device installed in the electronic apparatus, therefore, it is easy to generate Electromagnetic Interference (EMI) between the signal transmission structure and other electronic devices when transmitting the signals and further effect the signal transmission quality.
For example, in the semiconductor industry, the integrated circuit (IC) chip manufacturers usually produce high integration, multifunction and high speed IC chip by improving the clock frequency, the wiring density and the number of the I/O terminals. Generally, such an integrated circuit chip is electrically connected to a circuit board through a chip carrier in order to transmit the electronic signal between the integrated circuit chip and the circuit board. Nevertheless, the electronic signal is effected easily by EMI as the increasing clock frequency of integrated circuit chip.
FIG. 1 is a schematic view of a conventional package structure. Referring to FIG. 1, the conventional package structure 100 includes a carrier 110 used to carry a chip 10, a circuit board 120 parallel to the carrier 110, and a solder ball 130 that is electrically connected between a contact 112 of the carrier 110 and a contact 122 of the circuit board 120. Consequently, the electronic signal can transmit through the solder ball 130 between the chip 10 and circuit board 120.
It is to be noted that the carrier 110 is electrically connected to the circuit board 120 as well as parallel to the circuit board 120; thus, the carrier 110 and the circuit board 120 will form a resonant cavity. That is, if the clock frequency of the transmitting signal between the chip 10 and the circuit board 120 happens to the resonant frequency of the resonant cavity, parts of energy of the signal will transmit to the resonant cavity and the amplitude of the signal will be significantly decreased. It further causes poor signal transmission quality between the chip 100 and circuit board 120.
Moreover, when there is a noise happened in the carrier 110 and circuit 120 as well as the frequency of such noise is equivalent to the resonant frequency of the resonant cavity between the carrier 110 and the circuit board 120, the noise will interfere with the signal through the resonant cavity to cause the poor signal transmission quality between the chip 10 and the circuit board 120.